"Sober as a judge" is a simile that is used for someone who is completely sober. Anecdotal sources suggest that it first appeared in T. D'Urfey's Injured Princess in 1682 which says:
...fear me man, I am sober as a Judge. And how...
We also found that the phrase also appeared in Gettysburg, Pennsylvania on June 05, 1835 (Friday) at Peoples Press:
...thAi to one DAvid, while my heAd is AS SOBER AS A JUDGE. They were corned.....And only in obedience to his judgment SOBER reASon is not precipitAte; but..
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